The present invention relates to methods for estimating the weight of aircraft, and more particularly relates to estimating such weight without significantly moving the aircraft.
The estimation of the weight of an aircraft loaded with passengers, luggage, and other cargo is problematic and most methods rely on complex additional machinery to measure the load on the struts.
For example, in U.S. Patent Appl. Pub. No. 2007/012106 Mardirossian discloses a method and/or system for operating an aircraft, including (a) before an aircraft is loaded with passengers and luggage, performing a first measuring to measure a load on front landing gear strut(s) and rear landing gear strut(s) in order to obtain first weight data; and (b) after the aircraft has been loaded with passengers and luggage, performing a second measuring to measure a load on front landing gear strut(s) and rear landing gear strut(s) in order to obtain second weight data. Then, the first weight data is subtracted from the second weight data, while optionally compensating for fuel added to the aircraft between the times of the first and second measuring steps, in order to determine a total weight of the passengers and luggage on the aircraft. This total weight can be used in determining whether or not the plane is overloaded.
Similarly in U.S. Patent Appl. Pub. No. 2006/243855 Pradier discloses a method and device for determining the weight and/or a characteristic value of the position of the center of gravity of an aircraft standing on the ground by means of a plurality of undercarriages, each undercarriage including at least one structural element exhibiting a variable level of stresses depending on the fraction of the weight of the aircraft transmitted to the ground through the undercarriage. The method includes the steps of a) measuring on each undercarriage at least one parameter representing the stress level of the element; and b) evaluating the characteristic value and/or the weight according to the parameters measured in step a). At least one parameter measured in step a) is a magnetic or electrical characteristic of the structural element of the undercarriage.
Thus it can be seen that it would be advantageous to provide a method of weighing an aircraft without adding extra machinery to the aircraft, and to provide such data in an integrated, automated system capable of leveraging aircraft weight data to maximize performance or efficiency of the aircraft.
WO2005/035358 and WO2006/078322 disclose approaches to ground movement of aircraft by means of electric wheel motors. These utilize compact motor-generator machines able to provide high torque at low speed.
WO2005/112584 discloses a motor-generator machine comprising a slotless AC induction motor. The motor disclosed therein is an AC induction machine comprising an external electrical member attached to a supporting frame and an internal electrical member attached to a supporting core; one or both supports are slotless, and the electrical member attached thereto comprises a number of surface mounted conductor bars separated from one another by suitable insulation. An airgap features between the magnetic portions of core and frame. Electrical members perform the usual functions of rotor and stator but are not limited in position by the present invention to either role. The stator comprises at least three different electrical phases supplied with electrical power by an inverter. The rotor has a standard winding configuration, and the rotor support permits axial rotation.
WO2006/002207 discloses a motor-generator machine comprising a high phase order AC machine with short pitch winding. In the following, H is the harmonic order of a waveform, N is the number of turns in a winding, and A is the span value of a mesh connected stator winding. Disclosed therein is a high phase order alternating current rotating machine having an inverter drive that provides more than three phases of drive waveform of harmonic order H, and characterized in that the windings of the machine have a pitch of less than 180 rotational degrees. Preferably the windings are connected together in a mesh, star or delta connection.
The term ‘winding’ therein refers to the group of all of the windings and/or coils and/or conductors of a single phase, unless otherwise specified. The winding that constitutes each phase consists of a ‘supply half’ and a ‘back half’. The ‘supply half’ is driven by the power supply, and has a phase angle dependent on the power supply phase or phases to which it is connected. The phase angle of the back half of each phase is equal to the phase angle of the supply half, offset by 180 ED. The pitch of a winding is the number of rotational degrees between the supply half of the winding and the back half of the winding.
Recommended therein is a way of making the winding shorter and at the same time making the magnetomotive force more sinusoidal, by using short pitch windings, and by distributing the winding over several slots. When the coils of the winding are distributed over several slots, there is a reduction in the combined induced electromotive force. The individual coils of each winding will have a different spatial orientation due to the slots and there will be a phase difference between them.
Concentrated windings may also be used, wherein the coils of each half of a winding are contained in one slot only.
A method for operating a high phase order induction motor is also disclosed therein, involving electrically connecting N windings into a mesh connection with a value of A that provides a substantial range in speed/torque relation when operating with at least two out of first, second and third harmonic, low order harmonics being the most efficient.
The above disclosure is further directed to selection of a winding pitch that yields a different chording factor for different harmonics. The aim is to select a chording factor that is optimal for the desired harmonics.
WO2006/065988 discloses a motor-generator machine comprising stator coils wound around the inside and outside of a stator, that is, toroidally wound. The machine may be used with a dual rotor combination, so that both the inside and outside of the stator may be active. Even order drive harmonics may be used, if the pitch factor for the windings permits them.
In one embodiment of this motor-generator machine, an AC electrical rotating apparatus is composed of: a rotor, a substantially cylindrically shaped stator that has one surface that faces the rotor, and a number of conductive coils. Each coil is disposed in a loop wound toroidally around the stator. A drive means, for example an inverter, provides more than three different drive phases to the coils. In a further embodiment, the machine is equipped with teeth or slots for lending firm support to said coils. The slots may be on the stator surface that faces the rotor or also on the opposite stator surface. In a preferred embodiment, each of the coils is driven by a unique, dedicated drive phase. However, if a number of coils have the same phase angle as one another, and are positioned on the stator in different poles, these may alternatively be connected together to be driven by the same drive phase. In a further alternative, where two coils or more have a 180 electrical degree phase angle difference between them, they may be connected in anti-parallel to the same drive phase.
The AC machine coils may be connected and driven in a number of ways, including but not restricted to: a star connection and a mesh connection. It is preferable that the drive means, for example, the inverter, be capable of operating with variable harmonic drive, so that it may produce the impedance effect. In one embodiment, the coils are connected with short pitch windings. In a preferred embodiment, the coils are connected to be able to operate with 2 poles, or four poles, under H=1 where H is the harmonic order of the drive waveform. The coils may be connected together in series, parallel, or anti-parallel.
In U.S. Patent Appl. Pub. No. 2006/0273686, a motor-generator machine is disclosed comprising a polyphase electric motor which is preferably connected to drive systems via mesh connections to provide variable V/Hz ratios. The motor-generator machine disclosed therein comprises an axle; a hub rotatably mounted on said axle; an electrical induction motor comprising a rotor and a stator; and an inverter electrically connected to said stator; wherein one of said rotor or stator is attached to said hub and the other of said rotor or stator is attached to said axle.
Such a machine may be located inside a vehicle drive wheel, and allows a drive motor to provide the necessary torque with reasonable system mass. In one embodiment the stator coils are wound around the inside and outside of the stator. In a further embodiment, the machine contains a high number of phases, greater than three. In a further embodiment, the phases are connected in a mesh connection. In a further embodiment, each half-phase is independently driven to enable second harmonic drive for an impedance effect. Improvements are apparent in efficiency and packing density.
WO2006/113121 discloses a motor-generator machine comprising an induction and switched reluctance motor designed to operate as a reluctance machine at low speeds and an inductance machine at high speeds. The motor drive provides more than three different phases and is capable of synthesizing different harmonics. As an example, the motor may be wound with seven different phases, and the drive may be capable of supplying fundamental, third and fifth harmonic. The stator windings are preferably connected with a mesh connection. The system is particularly suitable for a high phase order induction machine drive systems of the type disclosed in U.S. Pat. Nos. 6,657,334 and 6,831,430. The rotor structure reacts to a particular drive waveform harmonic to produce a reluctance torque that rotates the rotor. For a different harmonic drive, substantially negligible reluctance torque is produced but induction based torque is produced to rotate the rotor. The rotor and stator may have a different high number of very small teeth causing the rotor to move much more slowly than the magnetic poles. The rotor may be designed with a number of salient poles or flux guides that produces substantial reluctance torque under the operation of a magnetic field of a certain pole count, but produces negligible reluctance torque, and substantial inductance-based torque, under the operation of a second magnetic field with a second pole count. The stator windings may be connected mesh or may be wrapped in a toroidal fashion around the stator.
It can be seen from the above that it would be advantageous to use such motor-generator machines in an aircraft undercarriage to estimate the weight of an aircraft, thereby providing extra functionality without adding extra machinery to an aircraft where space and weight are at a premium.